Callbag operator that applies a transformation on data passing through it. Works on either pullable or listenable sources.

The transformation may be a string containing a dot-notated path to get in a (nested) object. A default value may be passed to use if the full path does not exist or the value is undefined. (see the dlv module).

Otherwise, the transformation is assumed to be a function. In this case it works exactly like callbag-map.

npm install callbag-map-delve

const { pipe, fromIter, forEach } = require('callbag-basics');
const map = require('callbag-map-delve');
pipe(
  fromIter([ {person:{name:"Jason"}}, 
             {person:{name:"Monica"}}, 
             {} ]),
  map("person.name", "Unknown"),
  map(name => "Name: " + name),
  forEach(x => console.log(x))  // Name: Jason
                                // Name: Monica
                                // Name: Unknown
);